How to repair cinder block mortar joints

Written by edwin thomas
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How to repair cinder block mortar joints
This breeze block wall needs some mortar repair. (Jupiterimages/ Images)

Breeze blocks walls are frequently encountered in outbuildings such as garages and storage sheds, as well as in basements. Although the concrete breeze block itself is robust and can bear enormous weight, breeze block walls are erected using regular mortar mix, which can crack and crumble. Sometimes the damage to the mortar in a breeze block wall is minor and can be fixed with a little touching up, but in other cases the damaged joints should be repointed.

Skill level:
Moderately Easy

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Things you need

  • Acrylic mortar repair compound
  • Caulk gun (optional)
  • Cold chisel
  • Hammer
  • Wire brush
  • Mortar mix
  • Mortar bag
  • Trowel

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  1. 1

    Mend small cracks in the mortar with a tube of acrylic mortar repair compound. Put a bead of the compound into the crack and spread the top of the bead over the surface of the joint with a putty knife.

  2. 2

    Chip away the mortar for large cracks or crumbling areas using a hammer and a cold chisel. Remove mortar from the joint to at least 1 inch on both sides of the damaged area. Be careful not to chip or crack the breeze blocks.

  3. 3

    Scrape out any remaining bits of mortar from the joints to be worked on with a wire brush.

  4. 4

    Mix a batch of mortar in a bucket or other suitable container sufficient for 30 minutes worth of work. Pour this mortar into a mortar bag.

  5. 5

    Squeeze the mortar bag to push mortar through the bag's nozzle and fill the empty joints in the breeze block wall. The mortar bag works a lot like a cake decorator, so control the flow of mortar by adjusting your squeezing pressure.

  6. 6

    Scrape away extra mortar from the joint and then shape the mortar to match that of the original mortar in the surrounding joints.

Tips and warnings

  • Acrylic mortar repair compound comes in either cardboard or hard plastic tubes, which are used with a caulking gun just like caulk, or in small squeeze bottles. The only difference between the two formats is quantity.

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